Bone fixation assembly

ABSTRACT

A bone fixation system includes at least one bone fixation member and a bone fixation instrument. The bone fixation member includes a strap and a locking mechanism. The strap can be pulled through the locking mechanism so as to form a loop about a target bone so as to secure first and second bone segments in an approximated, compressed configuration. The bone fixation instrument is configured to apply tension to the loop about the target bone. The fixation instrument includes a tension assembly that is configured to secure a free end of the bone fixation member to the fixation instrument. The tension assembly is further configured to pull the free end so as to increase tension in the loop while the tension in the loop is less than a select tension. The tension assembly is unable to further increase tension in the bone fixation member once the tension in the bone fixation member has reached the select tension. The fixation instrument further includes a cutter assembly that is configured to cut the free end of the bone fixation member so as to separate the free end from the loop.

BACKGROUND

In order to provide access to certain internal anatomy, such as theheart during an open heart procedures, midline sternotomies aretypically performed. A midline sternotomy creates a cut substantiallyalong the midline of the sternum, thereby dividing the ribcage into twohalves and allowing the surgeon to move the ribcage so as to provideaccess to the heart. Upon completion of the open heart procedure, it isdesired to approximate and compress the sternum, and rigidly maintainthe sternal halves in their approximated position relative to each otherso that the sterna halves are prevented from moving with respect to eachother to promote bone fusion in the weeks following the surgicalprocedure.

During normal anatomical function, for instance during respiration, bodymovement, and carrying of objects, forces can be generated that act onthe sternum. One conventional system sternal fixation assembly includesstainless steel wires that are placed either parasternally (around thesternum) or transsternally (through the sternum bone) using a cuttingneedle that is attached to the wire, and subsequently twisted to tightenthe wire against the sternum. However, the twisting generates tensileforces onto the wires that tend to weaken the wire, which can result inbreakage both during the closure or post-operatively. Furthermore, thistype of system relies on the experience of the surgeon when tighteningthe wires. If the wires are not tightened enough, the sternalcompression can be compromised. If the wires are tightened too much, thewire can cut into or through the sternum and/or can break.

SUMMARY

In accordance with one embodiment, a bone fixation instrument isconfigured to apply tension to a bone fixation member so as to tightenthe bone fixation member about a target bone. The bone fixationinstrument includes a body that defiens a front end and an opposed rearend, a grip configured to secure a free end of the fixation member tothe fixation instrument, a traveler that is connected to the grip suchthat the grip moves rearward along with the traveler so as to increasetension in the bone fixation member, and an actuator operatively coupledto the traveler. The actuator can be configured to move from an initialposition toward a tension position in response to an applied force,thereby biasing the traveler to move rearward. The bone fixationinstrument can further include a tension limiter connected between theactuator and the traveler. The tension limiter allows the traveler tomove rearward when the tension in the bone fixation member is less thanthe selected tension, and prevents the traveler from moving rearwardwhen the tension in the bone fixation member reaches the selectedtension.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofthe preferred embodiments of the application, will be better understoodwhen read in conjunction with the appended drawings. For the purposes ofillustrating the present disclosure, there is shown in the drawingspreferred embodiments. It should be understood, however, that theapplication is not limited to the specific embodiments and methodsdisclosed, and reference is made to the claims for that purpose. In thedrawings:

FIG. 1 is a perspective view of a bone fixation instrument constructedin accordance with one embodiment;

FIG. 2A is a perspective view of a bone fixation member including a bodyand a locking member, showing the bone fixation member in an initialconfiguration;

FIG. 2B is an enlarged perspective view of a portion of the bonefixation member illustrated in FIG. 2A, showing the body insertedthrough the locking member so as to secure the bone fixation memberabout an underlying bone;

FIG. 3A is a perspective view of a plurality of the bone fixationmembers illustrated in FIG. 2A shown tightened about a target bone andcut;

FIG. 3B is a perspective view of the bone fixation instrumentillustrated in FIG. 1 operatively coupled to and tightening one of aplurality of the bone fixation members illustrated in FIG. 3A;

FIG. 3C is a perspective view of the bone fixation instrumentillustrated in FIG. 1 operatively coupled to and cutting one of thetightened bone fixation members illustrated in FIG. 3B;

FIG. 4 is a perspective view of the bone fixation instrument illustratedin FIG. 1, with portions removed to illustrate internal componentsincluding a tension assembly and a cutter assembly;

FIG. 5A is a perspective view of the bone fixation instrumentillustrated in FIG. 4, showing the cutter assembly in a cuttingposition;

FIG. 5B is a perspective view of a front end of the bone fixationinstrument as illustrated in FIG. 5A;

FIG. 6 is a perspective view of a rear end of the bone fixationinstrument illustrated in FIG. 4;

FIG. 7A is a perspective view of the front end of the bone fixationinstrument illustrated in FIG. 4, showing the tension assembly in adisengaged position;

FIG. 7B is a perspective view of the distal end of the bone fixationinstrument illustrated in FIG. 7A having portions removed and showingthe tension assembly in an engaged position;

FIG. 8A is a side elevation view of the bone fixation system, includingthe bone fixation instrument illustrated in FIG. 4 showing the bonefixation member as illustrated in FIG. 3A, with the target bone removedfor the purposes of illustration, shown loosely received in the bonefixation instrument with the tension assembly in the disengagedposition;

FIG. 8B is a side elevation view of the bone fixation system illustratedin FIG. 8A, showing the tension assembly in the engaged position suchthat the bone fixation instrument is secured to the bone fixationmember;

FIG. 8C is a side elevation view of the bone fixation system illustratedin FIG. 8B, showing the tension assembly in a tightened position;

FIG. 8D is a side elevation view of the bone fixation system illustratedin FIG. 8C, showing the tension assembly in a disengaged position afterhaving been previously in the tightening position FIG. 8C;

FIG. 8E is a side elevation view of the bone fixation system illustratedin FIG. 8D, showing the operation of a tension limiter whereby actuationof the tension assembly toward the tightened position does not tightenthe received bone fixation member;

FIG. 9 is a side elevation view of the bone fixation system illustratedin FIG. 8D, but showing actuation of the cutter assembly; and

FIG. 10 is a perspective view of a bone fixation instrument similar tothe bone fixation instrument illustrated in FIG. 4, but constructed inaccordance with an alternative embodiment.

DETAILED DESCRIPTION

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right”, “left”, “lower” and “upper”designate directions in the drawings to which reference is made. Thewords “proximally” and “distally” refer to directions toward and awayfrom, respectively, the surgeon using the surgical instrument. Thewords, “anterior”, “posterior”, “superior”, “inferior” and related wordsand/or phrases designate preferred positions and orientations in thehuman body to which reference is made and are not meant to be limiting.The terminology includes the above-listed words, derivatives thereof andwords of similar import.

Referring to FIGS. 1-3B, a bone fixation assembly 20 includes a bonefixation instrument 22 and at least one bone fixation member 24 such asa plurality of bone fixation members 24 that are configured to secure afirst and second bone segments 26 a and 26 b of a target bone 28, suchas a sternum, that are separated at a fracture location 30 together in acompressed approximated position.

In accordance with the illustrated embodiment, each bone fixation member24 can be substantially configured as a cable tie, and can include aflexible strap 32 defines a strap body 33 and has first end 34 a and asecond end 34 b opposite the first end 34 a along the length of thestrap 32, a needle tip 36 that extends from the first end 34 a, and alocking mechanism 38 that extends from the second end 34 b. The strap 32can be made from any suitable biocompatible material as desired, such asPEEK.

Each bone fixation member 24 can further include a first initiationregion 40 that extends from the first end 34 a toward the second end 34b along a portion of a length of the strap 32 (for instance,approximately ⅓ the length of the strap 32) and a second locking region42 that extends between the first initiation region 40 and the secondend 34 b. In accordance with the illustrated embodiment, the secondlocking region 42 extends from the first initiation region 40 to thesecond end 34 b. The first initiation region 40 can include a pluralityof small protrusions that extend out from the strap body 33 andalternate with recessed regions disposed between adjacent protrusions.Alternatively, the initiation region 40 can be substantially smooth anddevoid of protrusions or teeth. The second locking region 42 can includea plurality of locking teeth 48 that extend out from the strap body 33 adistance greater than the protrusions and are separated by recessedregions 51 disposed between adjacent locking teeth. It should beappreciated that the locking region 42 can extend along any portion upto all of the strap body 33 as desired.

The locking mechanism 38 includes a housing 50 a strap receiving slot 52that extends through the housing 50 and is configured to receive thefirst end 34 a of the strap 32. In accordance with the illustratedembodiment, the first end 34 a is inserted through the slot 52 so as todefine a loop 55 about the target bone 28. The locking mechanism 38 isconfigured to allow the strap 32 to translate unidirectionally throughthe slot 52 along the direction of Arrow A so as to reduce the size ofthe loop 55 about the first and second segments 26 a and 26 b of thetarget bone 28. For instance, the needle tip 36 can be inserted throughthe slot 52 and subsequently removed, for instance by cutting a neck 56of the strap body 33 that defines reduced thickness at a locationadjacent the needle tip 36, such that the strap 32 remains in the slot52. In accordance with the illustrated embodiment, the locking mechanism38 includes a locking member such as a tongue 54 that is connected tothe housing 50 and includes at least one complementary tooth such as aplurality of locking teeth 58 that extend into the slot 52. The lockingteeth 58 define a beveled leading edge 60 that that is configured to camover complementary beveled leading edges 49 of the locking teeth 48 whenthe strap 32 is translated through the slot 52 along the direction ofArrow A. The locking teeth 58 and 48 further define trailing edges 62and 47 that are sloped less than the beveled leading edges 60, such thatthe trailing edges 62 and 47 engage to prevent the strap 32 fromtranslating through the slot 52 along the direction opposite Arrow A,which would increase the size of the loop 55.

During operation, the strap 32 is wrapped around the first and secondsegments 26 a and 26 b of the target bone 28, and the needle tip 36 isinserted through the slot 52 and pulled through the slot 52 so as tocause the strap 32 to subsequently translate through the slot 52. Theneedle tip 36 can be removed from the strap 32, and the strap 32 canthen be further pulled, for instance manually, through the slot 52. Asthe strap 32 is translated through the locking mechanism 38 along thedirection of Arrow A, the small protrusions of the initiation region 40can slide through the slot 52 without engaging the locking teeth 58 ofthe locking mechanism 38. As the locking region 42 of the strap 32 istranslated through the slot 52 along the direction of Arrow A, thelocking teeth 48 and 58 can engage to prevent the tension that isinduced in the strap 32 from causing the strap 32 to back out of theslot 52 along a direction opposite Arrow A. For instance, as the strap32 translates through the locking mechanism 38 along the direction ofArrow A, the size of the loop 55 about the target bone 28 decreasesuntil tactile feedback indicates that tension has been induced in thestrap 32.

As illustrated in FIG. 3B, the fixation instrument 22 includes a tensionassembly 70 that is configured to secure the fixation instrument 22 tothe strap 32, and is further configured to further pull the strap 32through the locking mechanism 38 thereby further inducing tension in thestrap 32 until the strap 32 has securely compressed the bone first andsecond bone segments 26 a and 26 b of the target bone 28 together at thefracture location 30. As illustrated in FIG. 3C, the fixation instrument22 further includes a cutter assembly 72 that is configured to cut afree end 35 of the strap 32 that has passed through the lockingmechanism 38 once a desired tension has been induced in the strap 32about the first and second segments 26 a and 26 b of the target bone 28.For instance, the desired tension can be within a range defined by andbetween a lower end that can be approximately 50 Newtons orapproximately 80 Newtons, and an upper end that can be approximately150-160 Newtons or 200 Newtons. It should be appreciated that thedesired tension can depend on the bone quality and the preference of thesurgeon, and can for instance be any tension as desired that reliablysecures the target bone 28 without overtightening the strap 32.

Referring now to FIGS. 1 and 4, the fixation instrument 22 includes abody 76 that defines a front end 78 a and an opposed rear end 78 bspaced from the front end 78 a along a longitudinal direction L andopposed sides 80 that are spaced along a lateral direction A that issubstantially perpendicular with respect to the longitudinal directionL. The fixation instrument 22 further includes a handle 82 that issupported by the body 76, and can extend down from the body 76 along atransverse direction that is substantially perpendicular with respect toboth the longitudinal direction L and the lateral direction A. Inaccordance with the illustrated embodiment, the transverse direction Tis oriented vertically, and the longitudinal and lateral directions Land A are oriented horizontally, though it should be appreciated thatthe orientation of the fixation instrument may vary during use. Inaccordance with the illustrated embodiment, the body 76 is elongate inthe longitudinal direction L.

The fixation instrument 22 further includes a trigger 84 that extendsdown from the body 76 at a location spaced forward from the handle 82,and a nose 86 disposed at the front end 78a of the body 76. The handle82, the trigger 84, and the nose 86 can be discreetly attached to thebody 76 or integral with the body 76 as desired. The body 76 can includean outer housing 88 that includes a pair of housing members 90 a and 90b that are laterally opposed and define respective outer sides 92 andcan be joined together via fasteners such as screws 94 so as to supportthe various internal components of the fixation instrument 22.

It should be appreciated that the body 76 of the fixation instrument 22can be constructed in any suitable manner as desired. For instance, asillustrated in FIG. 1, the outer hosing members 90 a and 90 b caninclude a flange 93 that extends laterally inward toward each other fromthe sides 80 at a forward location of the body 76. Alternatively, asillustrated in FIG. 10, the flange 93 can extend further rearward andterminate adjacent an actuator 100.

For instance, the housing 88 can support the tension assembly 70 that isconfigured to tighten the bone fixation member, thereby inducing tensionin the bone fixation member 24, such as the strap 32, and can furthersupport the cutter assembly 72 that is configured to remove a free end35 of the bone fixation member 24 once the tension assembly 70 hasinduced a desired level of tension in the bone fixation member 24. Thetension assembly 70 includes a grip 96 that is movable between adisengaged position (FIG. 7A) whereby the grip 96 is configured toloosely receive the strap 32, such as the portion of the strap that haspassed through the locking mechanism 38, and an engaged position (FIG.7B) whereby the grip 96 is configured to be secured to the receivedstrap 32. The tension assembly 70 further includes a traveler 98 that isoperably coupled to the grip 96 and extends rearward from the grip 96,such that rearward movement of the traveler 98 causes the grip 96 tomove rearward in the secured configuration, thereby inducing tension inthe strap 32. The tension assembly 70 can further include an actuator100 such as the trigger 84 and a tension limiter 102 (FIG. 6) connectedbetween the trigger 84 and the traveler 98. The tension assembly 70 canfurther include a force transfer member 104 that is connected betweenthe trigger 84 and the tension limiter 102, thereby operatively couplingthe trigger 84 to the traveler 98.

During operation, and as described in more detail below, the free end 35of the strap 32 is received in the grip 96, the nose 86 is placedagainst the housing 50 of the locking mechanism 38, and the actuator 100is moved from an first initial position to a second grip position thatcauses the grip 96 to iterate from the disengaged position to theengaged position, and is further moved from the second grip position toa third tension position that causes the traveler 98 to move rearward,thereby inducing tension in the strap 32 when the tension in the strap32 is less than a select tension, which can be a desired maximum tensionas determined by the tension limiter 102. When the tension in the strap32 reaches the maximum tension, the tension limiter 102 prevents thetraveler 98 from moving rearward when the actuator 100 is moved to thetension position.

The cutter assembly 72 includes a cutter arm 106 movably supported bythe body 76 and a cutter blade 108 that is carried by the cutter arm106. The cutter arm 106 is movable from a seated disengaged position(see FIG. 4) whereby the cutter blade 108 is spaced from the free end 35of the strap 32 that is received in the grip 96 to an engaged position(see FIGS. 5A-B) whereby the cutter blade 108 cooperates with acomplementary cutter blade 87 of the nose 86 so as to cut the free end35 of the strap 32 (see FIG. 9). The fixation instrument 22, and inparticular the cutter assembly 72, further includes a safety mechanism110 that moves from a disengaged position, whereby the cutter arm 106can move from the seated disengaged position toward the engagedposition, and an engaged position that prevents the cutter arm 106 frommoving from the seated disengaged position toward the engaged position.

Referring now to FIGS. 4 and 7A-B, the traveler 98 of the fixationinstrument 22 can be provided as a longitudinally extending traveler rod111 that extends forward from the tension limiter 102 and supports thegrip 96 at its front end. The traveler rod can define a rectangularcross-section as illustrated in FIG. 4, a substantially circular crosssection as illustrated in FIG. 10, or any alternative size and shape asdesired. The grip 96 includes a first lower grip member 112 and a secondupper grip member 114 spaced from the lower grip member 112 so as todefine a gap 116 disposed between the lower and upper grip members 112and 114. The lower grip member 112 defines first grip surface 118 thatfaces the upper grip member 114, and can further define a plurality ofteeth 120 that extend out from the first grip surface 118 toward theupper grip member 114. The teeth 120 are configured to assist inreliably securing the grip 96 to the strap 32. The upper grip member 114is supported by the traveler rod 111 and defines a second grip surface115 that faces the first grip surface 118. The first and second gripsurfaces 118 and 115 can be sized and shaped as desired. In accordancewith the illustrated embodiment, the first grip surface 118 is curvedand substantially arc-shaped in accordance with the illustratedembodiment, such that the first grip surface 118 is convex with respectto the upper grip member 114. Furthermore in accordance with theillustrated embodiment, the second grip surface 115 is substantiallyflat.

The traveler rod 111 defines a forked first front end 117 a that definesa pair of laterally spaced side walls 122. The upper grip member 114 canbe rigidly supported by the traveler rod 111, and the lower grip member112 can be pivotally coupled to the traveler rod 111 at a pivot location113 about a laterally extending pivot pin 115 that defines a lateralpivot axis, and can further be disposed between the side walls 122. Thegrip 96 can further include a biasing member such as a torsion spring124 that biases the lower grip member to pivot in a forward directionabout the pivot location 113 toward the nose 86 from the disengagedposition of the grip 96 to the engaged position of the grip 96. The gripsurface 118 can extend eccentrically about the pivot location 113 suchthat the grip surface 118 moves upward toward the upper grip member 114as the lower grip member 112 pivots forward to the engaged position.

The lower grip member 112 defines a first or forward stop surface 126and the nose 86 defines a complementary second or rear stop surface 127.When the traveler rod 111 is in a forward position, the grip 96 is inthe disengaged position whereby the torsion spring 124 biases theforward stop surface 126 against the rear stop surface 127. When thegrip is in the disengaged position, the gap 116 is sized greater thanthe thickness of the free end 35 of the strap 32 as illustrated in FIG.7A. Accordingly, the free end of the strap 35 can be received in the gap116 between the first and second grip surfaces 118 and 115 asillustrated in FIG. 8A. As the traveler rod 111 moves rearward, thelower grip member 112 pivots forward about the pivot location 113 suchthat the grip surface 118 moves toward the grip surface 115 of the uppergrip member 114 as illustrated in FIG. 7B, thereby reducing the gap 116until the grip 95 captures the free end 35 of the strap 32 that isreceived in the gap 116 between the first and second grip surfaces 118and 115 under the force of the torsion spring 124 (FIG. 8B). It shouldthus be appreciated that as the traveler rod 111 further moves rearward,the free end 35 of the strap 32 will move rearward along with the grip95 and the traveler rod 111.

Referring now to FIGS. 4 and 6, the traveler rod 111 defines a secondrear end 117 b opposite the front end 117 a. The rear end 117 b of thetraveler rod 111 is connected to the tension limiter 102. The tensionlimiter 102 includes a spring member 128 such as a helical compressionspring that defines a first or front end 130 a and a second or rear end130 b. The spring member 128 is fixed with respect to movement relativeto the traveler rod 111 at its rear end 130 b, and movable with respectto the traveler rod 111 at its front end 130 a. The spring member 128 isfurther coupled to the trigger 84 at its front end. Thus, the springmember 128 is coupled to the trigger 84 at its end that is also movablewith respect to the traveler rod 111 so as to generate a force to thetraveler rod 111 that biases the traveler rod rearward away from thelocking mechanism 38 of the bone fixation member 24.

In accordance with the illustrated embodiment, the tension limiter 102includes a stationary end cap 129 that can be threaded onto or otherwisesecured to the traveler rod 111, for instance to the rear end 117 b ofthe traveler rod 111. The rear end 130 b of the spring member 128 isattached to the end cap 129 so as to secure the spring member 128 to thetraveler rod 111 at its rear end 130 b such that the rear end 130 b isfixed with respect to movement relative to the rod 111. Thus, as therear end 130 b of the spring member 128 moves rearward, the traveler rodmoves rearward along with the rear end 130 b of the spring member 128.The tension limiter 102 can further include a movable spring seat 132that is fixed to the movable front end 130 a of the spring member 128.In accordance with the illustrated embodiment, the traveler rod 111extends through the spring seat 132, such that the spring seat 132 ismovable in the longitudinal direction L along the traveler rod 111. Thetraveler rod 111 can define a longitudinally elongate slot 134 extendingtherethrough that can receive a projection of the spring seat 132. Thus,the slot 134 defines a length that allows the movable spring seat 132 totranslate from its forward-most position to its rearward-most position.

The tension assembly 70 further includes the force transfer member 104illustrated as a force transfer arm 136 that is pivotally connectedbetween the movable spring seat 132 and the trigger 84. Otherwisestated, the movable front end 130 a of the spring member 128 is coupledto the trigger 84 via the force transfer arm 136. In accordance with theillustrated embodiment, the force transfer arm 136 defines a front end138 a and an opposed rear end 138 b. The force transfer arm 136 ispivotally coupled, for instance at its rear end 138 b to the spring seat132 at a pivot location 139 that defines a lateral pivot axis. The forcetransfer arm 136 is further pivotally coupled, for instance at its frontend 138 a to the trigger 84 at a pivot location 140 that defines alateral pivot axis.

Referring again to FIG. 4, tension assembly 70 further includes thetrigger 84 that includes a lower grip portion 85 extending down from thehousing 88 at a location spaced forward of the handle 82 and an uppersecurement portion 89 pivotally connected to the force transfer arm 136and further pivotally connected to the housing 88. The trigger 84defines an aperture 91 that extends longitudinally through the uppersecurement portion 89 and receives the traveler rod that extends throughthe aperture, and thus the upper securement portion 89. The securementportion 89 of the trigger 84 is pivotally connected to the forcetransfer arm 136 at the pivot location 140, which defines a first lowerpivot location of the trigger 84. The securement portion 89 of thetrigger 84 is further pivotally coupled to the housing 88 at a secondupper pivot location 142 that defines a lateral pivot axis. The user cangrasp the handle 82 and the grip 85 of the trigger 84 with one hand, andsqueeze the trigger 84, which causes the trigger 84 to pivot rearwardabout the second upper pivot location 142. Because the lower pivotlocation 140 is disposed between the upper pivot location 142 and thegrip 85, the lower pivot location 140 moves rearward when the trigger144 is moved rearward by the user. The tension assembly 70 furtherincludes a spring member 146 that is connected between the handle 142and the trigger 144 that biases the trigger 144 forward to its initialposition. The fixation instrument 22 includes a stop member illustratedas a dowel 148 that extends laterally between the housing members 90 aand 90 b. The front edge of the securement portion 89 of the trigger 84abuts the dowel 148 so as to locate the trigger 144 in its first initialposition under the force of the spring member 146.

Operation of the fixation instrument will now be described with furtherreference to FIGS. 8A-E. For instance, as illustrated in FIGS. 7A and8A, the trigger 84, and thus the tension assembly 70, is in a firstinitial position whereby the front end 117 a of the traveler rod 111 isdisposed adjacent and proximate to the nose 86, such that the forwardstop surface 126 of the lower grip member 112 abuts the complementaryrear stop surface 127 of the nose 86, thereby causing the gap 116 todefine a transverse thickness greater than that of the free end 35 ofthe strap 32. The free end 35 is inserted into the gap 116 and the nose86 is positioned so as to abut the locking mechanism 38. The nose 86thus provides a brace member that prevents the locking mechanism 38 fromtraveling rearward when the fixation instrument 22 applies a rearwardforce to the free end 35.

When the tension assembly 70 is in the first initial position, thespring member 128 can be in an initial position that can be a neutralposition, or the movable spring seat 132 can be disposed at a forwardlocation with respect to the neutral position such that the initialposition of the spring member 128 can be flexed, such as slightlyextended, from its neutral position. For instance, the force of thespring member 146 that biases the trigger 84 forward can be greater thanthe force of the spring member 128 that biases the trigger 84 rearwardwhen the movable spring seat 132 is displaced forward from its neutralposition. When the spring member 128 is extended from its neutralposition, the spring member can apply a rearward compressive force ontothe end cap 129, and thus the traveler rod 111, which biases the lowergrip member 112 forward against the nose 86. It is appreciated that thetorsion spring 124 that biases the lower grip member 112 forward againstthe nose 86 creates an equal and opposite force against the traveler rod111 that biases the traveler rod rearwards. Thus, the forward force ofthe spring member 128 applied to the traveler rod 111 when the springmember 128 is slightly extended is greater than the rearward biasingforce of the torsion spring 124 against the traveler rod 111. Becausethe forward biasing force of the spring member 128 is greater than therearward biasing force of the torsion spring 124 when the spring member128 is slightly extended, the spring member 128 can actively maintainingthe grip 96 in its disengaged position.

Alternatively, the movable spring seat 132, and thus, the spring member128, can be in a neutral position when the tension assembly 70 is in thefirst initial position, such that the spring member 128 does not apply aforward biasing force or a rearward biasing force to the traveler rod111. As described above, the torsion spring 124 can apply a force to thetraveler rod 111 that biases the traveler rod rearwards 111. However,rearward movement of the traveler rod 111 would cause the rear end 130 bof the spring member 128 to move away from the front end 130 a of thespring member 128, thereby causing the spring member 128 extend from itsneutral position. The spring member 128 can have an spring constant thatis greater than the spring constant of the torsion spring 124 such thatthe spring member 128 resists extension under the forces of the torsionspring 124, and thereby passively maintains the lower grip member 112 inits disengaged position whereby the forward stop surface 126 restsagainst the complementary rear stop surface 127 of the nose 86 and thegap 116 is thus thicker in the transverse direction T than the free end35 of the strap 32 that is received in the gap 116.

Referring now to FIGS. 4 and 8B, when the user applies a rearwarddirected force F to grip portion 85 of the trigger 84, the trigger 85and thus also the tension assembly 70 moves from the first initialposition to the second grip position that causes the grip 96 to iteratefrom the disengaged position to the engaged position. In accordance withthe illustrated embodiment, the rearward force applied to the gripportion 85 of the trigger 84 causes the trigger 84 to pivot rearwardabout the upper pivot location 142, which causes the lower pivotlocation 140 to move rearward. It should be appreciated that the lowerpivot location 140 moves rearward about an arc-shaped travel path aboutthe upper pivot location 142. Rearward movement of the lower pivotlocation 140 causes the force transfer arm 136 to likewise movesrearward, thereby transferring the force from the trigger to the movablespring seat 132 and the front end 130 a of the spring member 128. Itshould be appreciated that the force transfer arm 136 pivots relative tothe trigger 84 about the lower pivot location 140 as the force transferarm 136 moves rearward.

As the force transfer arm 136 moves rearward, the force transfer arm 136further causes the movable spring seat 132 and the front end 130 a ofthe spring member 128 to translate rearward along the travel rod 111 inthe longitudinal direction L toward the rear end 130 b of the springmember 128, thereby flexing the spring member 128 from the first initialposition. It should be appreciated that the force transfer arm 136pivots relative to the movable spring seat about the pivot location 139.As the front end 130 a of the spring member 128 moves rearward towardthe rear end 130 b of the spring member 128, the spring member 128flexes from its neutral position so as to apply a rearward biasing forceto the traveler rod 111. In accordance with the illustrated embodiment,the spring member 128 compresses when the end 130 a of the spring member128 moves rearward, and thus biases the end 130 b, the end cap 129, andalso therefore the traveler rod 111 to move rearward. Alternatively, themovement of the end 130 a of the spring member 128 can be sufficient soas to reduce the force of the spring 128 that biases the traveler rod111 to a level that is less than the force of the torsion spring 124that biases the traveler rod 111 rearward. The fixation instrument 22can define an aperture 119 that extends through the rear end 78 b of thebody 76. The aperture 119 is sized to receive the end cap 129 such thatthe end cap 129 can extend beyond the housing 88 due to rearward travelof the rear end 130 b of the spring member 128.

Accordingly, referring also to FIGS. 7A-B, the traveler rod 111 isbiased, under a biasing force applied by the torsion spring 124, thespring member 128, or both to move rearward away from the nose 86. Asthe rod 111 moves away from the nose 86, the torsion force of thetorsion spring 124 causes the lower grip member 112 to pivot forwardabout the pivot location 113 along the direction of Arrow B so as toreduce the gap 116 until the grip surfaces 118 and 115 capture the freeend 35 of the strap 32 in the gap 116, thereby securing the free end 35to the fixation instrument 22 while the nose 86 abuts the loop 55, andin particular the housing 50 of the locking mechanism 38. Thus, it canbe said that moving the trigger 84 from the first neutral position tothe second neutral position causes the grip 96 to iterate from itsdisengaged position to its engaged position

Referring now to FIGS. 4, 6, and 8C, continuous application of the forceF to the grip portion 85 of the trigger 84 causes the trigger 84 tofurther pivot about the upper pivot location 142, thereby causing thetrigger 84, and thus the tension assembly 70, to move from the secondgrip position to a third tension position that causes the traveler 98 tomove rearward, thereby applying tension to the free end 35 of the strap32 when the tension in the strap 32 is less than the desired tension,such as a maximum tension as determined by the tension limiter 102.Because engagement of the nose 86 of the fixation instrument 22 with theloop 55, and in particular the housing 50 of the locking mechanism 38,provides a brace that prevents the loop 55 from moving rearward alongwith the free end 35, when the tension assembly 70 places the free end35 in tension, the strap 32 and in particular the locking region 42 isfurther pulled through the locking mechanism 38. As described above withreference to FIG. 2B, the locking teeth 58 and 48 engage so as to allowthe locking region 42 to be pulled through the locking mechanism so asto reduce the size of the loop 55 or to place the loop 55 in furthertension about the bone segments that are disposed in the loop 55.Whether the size of the loop 55 is reduced or whether the loop 55 isfurther tightened about the bone segments disposed in the loop, it canbe said that the fixation instrument places the bone fixation member 24in tension when the tension assembly moves from the second grip positionto the third tension position.

Accordingly, once a trigger stroke has been completed whereby thetrigger 84 has been moved to its rearward-most position as illustratedin FIG. 8C, the user can release the trigger 84 which causes the springmember 146 to bias the trigger 84 to its forward position shown in FIG.8D. Once the trigger 84 has moved to its forward position, the trigger84 and thus the tension assembly 70 are in the first initial position,such that the lower grip member 112 is biased against the nose 86thereby placing the grip 96 in its disengaged position as describedabove. Accordingly, while the free end 35 of the strap 32 is no longersecured to the fixation instrument 22, the engagement of the lockingteeth 58 and 48 prevent the increased tension induced in the loop 55from allowing the free end 35 to move through the housing in a directionopposite Arrow A that would reduce the tension in the loop 55.

It should be appreciated that the motion of the trigger 84 from thesecond grip position to the third tension position can be a continuationof the movement from the first initial position to the second gripposition. Thus, the trigger 84 can move from the first initial positionto the second grip position to the third tension position in a singlefluid motion.

The nose 86 can again be placed in contact with the locking mechanism 38and the free end 35 can be received in the gap 116 of the grip 96, andthe tension assembly 70 can be iterated from the first initial positionto the second grip position to the third tension position as many timesas desired, for instance until the tension induced in the loop 55reaches a predetermined maximum tension. When the tension in the loop 55reaches the maximum tension, the tension limiter 102 prevents thetraveler 98 from moving rearward when the actuator 100 is moved to thetension position.

For instance, referring now to FIGS. 4, 6, and 8E, it should beappreciated that the spring member 128 has a spring constant that isconfigured to apply a predetermined biasing force to the traveler rod111 when the front end 130a of the spring member 128 has translatedrearward a distance corresponding to full rearward actuation of thetrigger 84. Accordingly, so long as the tension in the loop 55 is lessthan the desired force as defined by the spring member 128 and length oftravel of the front end 130 a of the spring member 128, compression ofthe spring member 128 will cause the force applied by the spring member128 to move the traveler rod 111 rearwards. However, once the tensioninduced in the loop 55 reaches the desired force, compression of thespring member 128 due to rearward movement of the front end 130 a willcause the spring member 128 to apply a rearward biasing force againstthe traveler rod 111 that is insufficient to overcome the forcenecessary to further tighten the loop 55.

It should appreciated that the spring member 128 can be configured toapply a rearward biasing force against the traveler rod 111 that isgreater than the tension induced in the loop 50 about the target bone28. For instance, the spring member 128 can apply a force that issufficient to overcome both the tension of the loop 50 and theadditional force that causes one or both of the locking teeth 48 and 52to deflect as the teeth ride over each other when tightening the loop55. Accordingly, the tension limiter 102 can be configured apply a forcethat is greater than, but corresponds to, the tension in the loop 55about the target bone. Thus, the maximum force applied by the tensionlimiter 102 can correspond to the maximum desired tension in the loop55, it being appreciated that once the teeth 48 and 52 ride over andpast each other, the tension in the loop 55 can decrease somewhat as theteeth 48 and 52 interlock. In accordance with one embodiment, thetension limiter 102 can apply a maximum force as desired, for instanceup to approximately 430 Newtons or any other force as desired thatcorresponds to a desired maximum tension in the loop 55 about the targetbone 28. As a result, once the desired maximum tension in the loop 55has been induced about the target bone 28, the force applied by thetension limiter 102 when the trigger 84 is fully actuated isinsufficient to cause the teeth 48 and 58 to ride past each other andfurther tighten the loop 55. Accordingly, once the maximum tension inthe loop 55 has been induced about the target bone 28, the force appliedby the tension limiter 102 will be insufficient to cause the travelerrod 111 to translate rearward a sufficient distance that furthertightens the loop 55 about the target bone 28.

It should be appreciated that the spring member 128 can alternatively beconfigured as an extension spring. For example, in accordance with analternative embodiment, the front end 130 a can be connected to thetraveler rod 111 and fixed with respect to the traveler rod 111, and therear end 130 b can be movable relative to the traveler rod 111. Forinstance, the rear end 130 b can be coupled to the trigger 84 via theforce transfer member 104 in the manner described above. The tensileforce applied to the rear end 130 b and corresponding rearwarddisplacement of the rear end 130 b can thus cause the spring force tobias the traveler rod 111 to move rearward, thereby inducing tension inthe strap 32 in the manner described above. Thus, the initial positionof the spring member 128 initial position that can be a neutral positionas described above, or the initial position of the spring member 128 canbe flexed, such as slightly compressed, from its neutral position.

Referring now to FIGS. 4-5B, the fixation device 22 includes a cutterassembly 72 that includes a cutter arm 106 having a front end 107 a anda rear end 107 b, and a movable cutter blade 108 carried by the cutterarm 106, for instance at the front end 107 a. The cutter arm 106 can besized and shaped as desired, and is constructed in accordance with theillustrated embodiment such that the front and rear ends 107 a and 107 bextend substantially longitudinally. The cutter arm 106 can also includean offset segment 107 c that extends laterally outward along a forwarddirection from the rear end 107 b toward the front 107 a. Thus, thefront end 107 a can be offset laterally outward with respect to the rearend 107 b. For instance, the rear end 107 b can be disposed between theopposed sides 80 and the front end 107 a can be coupled to one of theside 80 at a location laterally outward of the side 80. The cutter arm106 can further include an intermediate longitudinal segment 107 d thatextends forward from the offset segment 107 c and is thus extendssubstantially parallel to the front and rear ends 107 a and 107 b. Thecutter arm can also include a transversely offset segment 107 e thatextends between the intermediate longitudinal segment 107 d and thefront end 107 a, and extends transversely down along a forwarddirection. Accordingly, the front end 107 a can be transversely offsetwith respect to the rear end 107 b. The cutter arm 106 can furtherinclude a grip 150 at disposed at the rear end 107 b.

Referring also to FIG. 6, the cutter assembly 72 can include a seat 158that receives the cutter arm 106 at an upper end of the body 76 when thecutter arm 106 is in its disengaged position. In accordance with theillustrated embodiment, the seat 158 is sized and shaped so as toreceive the cutter arm 160. Accordingly, when the cutter arm 106 isseated in the seat 158, the cutter arm 106 can be said to be in a seateddisengaged position. The seat 158 can further include at least oneretainer member 162, such as a pair of laterally opposed retainermembers 162 that are spaced apart a distance slightly less than thelateral thickness of the cutter arm 106. The retainer members 162 can bespring loaded to the position spaced apart a distance slightly less thanthe lateral thickness of the cutter arm 106. For instance, the cutterarm 106 can define a recess 164 that is sized to receive the retainermembers 162 when the cutter arm 106 is in its seated disengagedposition. Accordingly, when moving the cutter arm 106 to and from itsseated disengaged position, an engagement force along the direction ofArrow C can be applied to the cutter arm 106 that is sufficient toovercome the retention force of the retainer members 162, which causesthe retainer members 162 to pop out of the recess 164 and free thecutter arm 106 from the seat 158.

Referring also to FIGS. 7A-B, the cutter arm 106 can be pivotallyattached to the body 76, for instance at one of the sides 80. Inaccordance with the illustrated embodiment, the cutter arm 106 ispivotally attached at its front end 107 a to the nose 86 at a pivotlocation 152 that defines a lateral pivot axis. For instance, the cutterassembly 72 can include a blade support body 154 that is substantiallycylindrical and extends through a side wall of the nose 86 and rotatableabout its central axis so as to allow the cutter arm 106 to pivotbetween its engaged position and its disengaged position. When thecutter arm 106 is in its disengaged position, the cutter blade 108 isspaced above a complementary and substantially stationary cutter blade87 of the nose 86 so as to define a gap 156 that has a transversedimension greater than that of the free end 35 of the strap 32 so thatthe free end 35 is loosely received in the gap 156, which is disposedforward with respect to the grip 96, and thus the gap 116.

Referring again to FIGS. 5A-B, the cutter arm 106 can be pivoted up andforward about the pivot location 152 along the direction of Arrow C toits engaged position, which causes the cutter blade 108 to travel downalong an arc-shaped path toward the complementary cutter blade 87 so asto reduce the size of the gap 156. The cutter blade 108 is recessedrearward with respect to the complementary cutter blade 87 such that thecutter blade 108 slides past the cutter blade 87. Accordingly, thecutter blades 108 and 87 cooperate so as to cut the free end 35 of thestrap 102 that is received in the gap 156 as the cutter blade 108 slidespast the cutter blade 87 (see FIG. 9). Accordingly, when the nose 86abuts the locking mechanism 38 of the bone fixation member 24 such thatthe gap 156 is aligned with the outlet end of the strap-receiving slot52 of the housing 50 of the locking mechanism (see FIGS. 2B and 3C) andthe arm 106 is moved to its engaged position, the cutter assembly 72 cancut the free end 35 at a location that is spaced from the housing 50 adistance substantially equal to the distance between the front end ofthe nose 86 and the cutter blade 108. Therefore, once the fixationinstrument 22 has applied the desired amount of tension in the strap 32,the free end 35 can be cut in the manner described above tosubstantially remove the free end 35 from the loop 55.

Referring now to FIGS. 4 and 6, the cutter assembly 72 further includesa safety mechanism 110 that moves from a disengaged position, wherebythe cutter arm 106 can move from the seated disengaged position towardthe engaged position, and an engaged position that prevents the cutterarm 106 from moving from the seated disengaged position toward theengaged position. In accordance with the illustrated embodiment, thecutter assembly 72 includes a first engagement member 166 that extendsdown from the cutter arm 106 and a second engagement member 168 thatextends up from the movable spring seat 132. When the tension assembly70 is in the first initial position, the first engagement member 166 isspaced rearward from the movable spring seat 132. Otherwise stated, thefirst engagement member 166 is spaced from the movable spring seat 132in the direction that the spring seat 132 moves when the tensionassembly 70 is moved from the first initial position toward the thirdtension position. Accordingly, second engagement member 168 can movetoward the first engagement member as the movable spring seat 132 movesrearward. Alternatively, the second engagement member 168 can extendfrom the traveler rod 111 and movable along with the traveler rod 111 soas to interlock with the engagement member 166.

The first and second engagement members 166 and 168 are configured so asto interlock when they longitudinally overlap. For instance, the secondengagement member 168 can be configured as a housing 170 having a slot172 that receives the first engagement member 166. The first engagementmember 166 can define a flange 174 that overlaps the housing 170 in thetransverse direction, such that the flange 174 abuts the housing 170when an engagement force is applied to the cutter arm 106 along thedirection of Arrow C so as to move the cutter arm 106 from its seateddisengaged position toward its engaged position. In accordance with theillustrated embodiment, the first and second engagement members 166 and168 interfere so as to prevent the cutter arm 106 from being unseatedfrom the seat 158. It should be appreciated that the first engagementmembers 166 and 168 can alternatively be sized and shaped as desired soas to selectively interfere with each other in the manner describedherein.

Referring also to FIG. 8A, when the tension assembly 70 is in the firstinitial position, the first and second engagement members 166 and 168are longitudinally spaced apart such that the cutter arm 106 can bemoved from the seated disengaged position to the engaged position alongthe direction of Arrow C. When the tension assembly 70 moves to thesecond grip position, the movable spring seat 32 translateslongitudinally rearward, thereby also translating the second engagementmember 168 longitudinally rearward toward the first engagement member166. In accordance with the illustrated embodiment illustrated in FIG.8B, the engagement members 166 and 168 remain longitudinally spaced fromeach other when the tension assembly 70 is in the second grip position,thereby allowing the cutter arm 106 to become unseated and move from thedisengaged position toward the engaged position. Accordingly, referringto FIG. 9, after the fixation instrument 22 has induced a desired amountof tension in the loop 55, the tension assembly 70 can be moved to thegrip position so as to capture the free end 35 in the gap 116 prior tocutting the free end 35 in the manner described above. Thus, asillustrated in FIG. 3A, the plurality of bone fixation members 24 can betightened about the target bone 28 by actuating the tension assembly 70as described herein, and can be subsequently cut by actuating the cutterassembly 72 as described herein.

In accordance with the illustrated embodiment shown in FIG. 8C, theengagement members 166 and 168 are positioned so as to overlap when thetension assembly 70 has moved from the second grip position toward thethird tension position. Thus, once the tension assembly 70 has advancedbeyond the second grip position, the engagement members 166 and 168interfere when the engagement force is applied to the cutter arm 106along the direction of Arrow C. Therefore, the safety mechanism 110prevents the fixation instrument 22 from cutting the free end 35 whilethe tension assembly 70 is applying tension to the strap 32.Alternatively, the engagement members 166 and 168 can be positioned soas to at least partially overlap and interlock when the tension assembly70 is in the second grip position, thereby defining an interference thatprevents the cutter arm 106 fro m becoming unseated and moving to theengagement position along the direction of Arrow C.

Although the disclosure has been described in detail, it should beunderstood that various changes, substitutions, and alterations can bemade herein without departing from the spirit and scope of the inventionas defined by the appended claims. Moreover, the scope of the presentdisclosure is not intended to be limited to the particular embodimentsdescribed in the specification. As one of ordinary skill in the art willreadily appreciate from the disclosure of the present invention,processes, machines, manufacture, composition of matter, means, methods,or steps, presently existing or later to be developed that performsubstantially the same function or achieve substantially the same resultas the corresponding embodiments described herein may be utilizedaccording to the present disclosure.

1.-22. (canceled)
 23. A method for securing a bone fixation memberaround a target bone via a bone fixation instrument comprising: securinga free end of the bone fixation member to a tension assembly of saidbone fixation instrument, the tension assembly being configured tosecure the fixation instrument to the free end of the bone fixationmember, wherein the tension assembly is unable to further increasetension in the bone fixation member once the tension in the bonefixation member has reached the select tension; activating the tensionassembly to in order to pull the free end of the bone fixation memberand increase tension in the bone fixation member about the target boneuntil the tension in the bone fixation member has reached a selecttension, wherein the tension assembly is unable to further increasetension in the bone fixation member once the tension in the bonefixation member has reached the select tension; and, actuating a cutterassembly of said fixation instrument, wherein said cutter assembly isactuatable independently of whether the tension in the bone fixationmember has reached the select tension.
 24. The method according to claim23, wherein the bone fixation instrument further comprises a tensionlimiter for setting the select tension and for preventing the tensionassembly from further increasing tension in the bone fixation memberonce the tension therein has reached the select tension by applying aforce that counteracts the tension applied by the tension assembly. 25.The method according to claim 23, wherein the tension assembly furthercomprises a grip that is configured to move from 1) a disengagedposition wherein the grip is configured to loosely receive the free endof the bone fixation member to 2) an engaged position wherein the gripsecures the free end of the bone fixation member to the bone fixationinstrument, and, wherein the grip and the cutter assembly are bothsubstantially aligned along the longitudinal axis of the bone fixationinstrument.
 26. The method according to claim 25, wherein the tensionassembly further comprises a traveler that is operably coupled to thegrip such that rearward movement of the traveler causes the grip to moverearward in the engaged position, thereby inducing tension in the strap.27. The method according to claim 26, wherein said traveler issubstantially aligned along the longitudinal axis of the bone fixationinstrument.
 28. The method according to claim 23, wherein the bonefixation instrument further comprises a safety mechanism that preventsactuation of the cutter assembly when the tension assembly has pulledthe free end so as to increase tension in the bone fixation member. 29.A method for securing a bone fixation member around a target bone via abone fixation instrument, the method comprising the steps of wrappingthe bone fixation member about the target bone, and securing a free endof the bone fixation member to a grip of the bone fixation instrument;causing a traveler of the fixation instrument that is connected to thegrip to move away from the target bone, thereby causing the grip toincrease tension in the bone fixation member until the tension in thebone fixation member has reached the select tension; preventing thetraveler from moving further away from the bone once the tension in thebone fixation member has reached the select tension; and actuating acutter assembly of the bone fixation instrument to cut said bonefixation member after the causing step.
 30. The method according toclaim 29, wherein the traveler is prevented from moving further awayfrom the bone using a tension limiter that is connected between anactuator and the traveler.
 31. The method according to claim 30, whereinthe tension limiter is a spring member, and wherein movement of theactuator causes the spring member to flex and bias the traveler rearwardunder a biasing force.
 32. The method according to claim 30, wherein thetraveler moves rearward when the biasing force is greater than thetension in the bone fixation member.
 33. The method according to claim32, wherein the traveler remains stationary when the biasing force isnot greater than the tension in the bone fixation member.
 34. The methodaccording to claim 30, wherein the body extends along a longitudinaldimension.
 35. The method according to claim 34, wherein the travelerand the tension limiter are both substantially aligned along thelongitudinal dimension of the body.
 36. The method according to claim30, wherein the tension limiter prevents the tension assembly fromfurther increasing tension in the bone fixation member once the tensiontherein has reached the select tension by applying a force thatcounteracts the traveler.
 37. The method according to claim 29, furthercomprising using a safety mechanism to prevent actuation of the cutterassembly when the traveler has moved rearward so as to increase tensionin the bone fixation member